This invention relates generally to thin-film electrochemical cells and, more particularly, to thin-film electrochemical cells that are formed using sheets of a discontinuous cathode structure and methods and apparatuses for producing same.
Various lamination apparatuses and processes have been developed to produce electrochemical cells fabricated from thin-film materials. Many conventional lamination approaches employ a cutting mechanism that cuts a sheet of electrochemical cell material into small segments. The individual segments are then manually or mechanistically aligned and layered as part of a separate lamination process. The layered structure is then subjected to lamination forces by an appropriate force producing mechanism.
Notwithstanding the variety of conventional lamination and stacking approaches currently available, many of such approaches are not well suited for applications which require relatively high levels of productivity, automation, and flexibility. For example, many conventional lamination processes are unable to accommodate electrochemical cell materials of varying types, sheet sizes, and sheet shapes. Many of such available lamination techniques are not well suited nor adaptable to autonomously and continuously laminate multiple webs of differing materials, as is typically necessary in the construction of thin-film electrochemical laminate structures, for example.
There exists a need for an improved apparatus and method for laminating films and sheet materials of varying types, shapes, and sizes. There exists a particular need for an improved apparatus and method for laminating layers of electrochemical cell materials and for producing electrochemical half cells and unit cells for use in the construction of solid-state, thin-film batteries. The present invention fulfills these and other needs.
The present invention is directed to thin-film electrochemical halfcells and full cells that incorporate a unique discontinuous cathode sheet structure. The present invention is further directed to methods and apparatuses for producing same.
According to one embodiment of the present invention, a thin-film monoface electrochemical cell structure includes a cathode sheet layer comprising a series of discontinuous cathode sheets. Each of the cathode sheets includes a cathode layer and a current collector layer having a first surface contacting a first surface of the cathode layer. A gap is defined between adjacent ones of the cathode sheets. A solid electrolyte layer contacts a second surface of the cathode layer and extends across the gaps defined between the adjacent cathode sheets.
In one configuration, an electrical insulator layer contacts a second surface of the current collector layer. The electrical insulator layer extends across the gaps defined between the adjacent cathode sheets.
The solid electrolyte layer preferably encompasses a perimeter of each of the cathode layer of the cathode sheets. For example, the first edge of the solid electrolyte layer preferably extends beyond the first edge of the cathode layer, and a second edge of the solid electrolyte layer extends beyond a second edge of the cathode layer.
The current collector layer includes a first edge and a second edge, and the cathode layer includes a first edge and a second edge. The first edge of the current collector layer preferably extends beyond the first edge of the cathode layer and the first edge of the solid electrolyte layer, respectively. In one configuration, the second edge of the current collector layer extends beyond the second edge of the cathode layer and the second edge of the solid electrolyte layer.
In one arrangement, the series of discontinuous cathode sheets is arranged in a number of rows to define a matrix of the discontinuous cathode sheets. In such an arrangement, a first gap is provided in a transverse direction between adjacent discontinuous cathode sheets, and a second gap is provided in a longitudinal direction between adjacent rows of the discontinuous cathode sheets.
The cathode layer typically comprises a cathode active material, an electrically conductive material, an ionically conducting polymer, and an electrolyte salt. For example, the cathode layer can include a vanadium oxide material or a lithiated vanadium oxide material. In one particular embodiment, the cathode layer includes a cathode active material selected from the group consisting of LiCoO2, LiNiO2, LiMn2O4, Li[M(1xe2x88x92x)Mnx]O2 where 0 less than x less than 1 and M represents one or more metal elements, polyacetylene, polypyrrole, polyaniline, polythiophene, MoS2, MnO2, TiS2, NbSe3, CuCl2, a fluorinated carbon, Ag2CrO4, FeS2, CuO, Cu4O(PO4)2, sulfur, and polysulfide.
The electrolyte layer preferably comprises a solid polymer electrolyte layer. In one configuration, the solid electrolyte layer comprises a random polyether copolymer of ethylene oxide and an ether oxide selected from the group consisting of propylene oxide, butylene oxide, and alkylglycidylether. In another configuration, the solid electrolyte layer comprises a crosslinked solid ionically conductive polymer comprising urethane groups, urea groups, thiocarbamate groups, or combinations thereof and inorganic particles.
In accordance with a further configuration, the solid electrolyte layer comprises a first surface and a second surface, such that the first surface of the solid electrolyte layer contacts the second surface of the cathode layer. The structure further includes an anode layer that contacts the second surface of the solid electrolyte layer. The anode layer preferably comprises lithium. An electrical insulator layer is typically included to contact a second surface of the current collector layer in this configuration.
According to another embodiment of the present invention, a thin-film biface electrochemical cell structure includes a cathode sheet layer comprising a series of discontinuous cathode sheets. Each of the cathode sheets includes a first cathode layer having a first surface and a second surface. A second cathode layer includes a first surface and a second surface. A current collector layer is disposed between the respective first surfaces of the first and second cathode layers. A gap is defined between adjacent ones of the cathode sheets. A first solid electrolyte layer contacts the second surface of the first cathode layer and extends across the gaps defined between the adjacent cathode sheets. A second solid electrolyte layer contacts the second surface of the second cathode layer and extends across the gaps defined between the adjacent cathode sheets. A biface cell structure according to this embodiment preferably include many of the features previously described with regard to a monoface cell structure.
In accordance with a further embodiment of the present invention, a method of producing a series of thin-film electrochemical cell structures involves cutting a web (cathode web), comprising a cathode layered structure, moving at a first speed into a series of cathode sheets. A web (electrolyte web) of a solid electrolyte is moved at a second speed equal to or greater than the first speed. Each of the cathode sheets moving at the first speed is laminated with the electrolyte web moving at the second speed to produce a first laminate structure having a space between adjacent cathode sheets. A web (third web) of a material is laminated with the first laminate structure such that the cathode sheets are disposed between the electrolyte web and the third web.
In accordance with a biface cell configuration, the material of the third web comprises a solid electrolyte. According to a monoface cell configuration, the material of the third web comprises an electrical insulator.
Cutting the cathode web preferably involves rotatably cutting the cathode web. Laminating each of the cathode sheets preferably involves rotatably laminating each of the cathode sheets with the electrolyte web. Laminating the third web of the material preferably involves rotatably laminating the third web of the material with the first laminate structure.
According to one approach, cutting the cathode web involves cutting a portion of the cathode web and removing excess cathode web. The space between adjacent cathode sheets in this case is a function of one or both of a size and shape of the removed excess cathode web.
The cathode web, according to one configuration, comprises a number of down-web directed rows of the cathode layered structure. Cutting the cathode web in this case involves cutting the cathode web in a cross-web direction to produce a matrix of the cathode sheets.
Each of the cathode sheets is defined by a length, and cutting the cathode web involves cutting the cathode web with a rotary die, such that the length of each cathode sheet is a function of the first speed of cathode web movement relative to the second speed of the rotary die. The length of each cathode sheet can also be a function of the first speed of cathode web movement relative to a circumferential die blade spacing and the second speed of the rotating die blade.
The space or gap between adjacent cathode sheets is a function of the first speed of cathode web movement relative to the second speed of the electrolyte web. For example, cutting the cathode web typically involves cutting the cathode web with at least one rotating die blade separated by a circumferential blade spacing (D). The space (S) between adjacent cathode sheets in this case is a function of the first speed (W1) of cathode web movement relative to the circumferential die blade spacing (D) and the second speed (W2) of the rotary die blade. The space (S) between adjacent cathode sheets, in this case, is characterized by an equation S=D((W2/W1)xe2x88x921).
The lamination method according to this embodiment may further involve laminating a web (lithium web) of lithium material with the electrolyte web. This method further involves cutting through the lithium web, third web, and electrolyte web at respective locations in alignment with the space between adjacent cathode sheets. Cutting through the respective lithium, third, and electrolyte webs preferably involves rotatably cutting through the respective lithium, third, and electrolyte webs. The electrolyte web may further include a carrier web. Cutting through the respective lithium, third, and electrolyte webs in this case involves rotatably cutting through the respective lithium, third, and electrolyte webs but not cutting entirely through the carrier web.
In accordance with another embodiment of the present invention, an apparatus for producing a series of thin-film electrochemical cell structures includes a first feed station that feeds a web (cathode web), comprising a cathode layered structure, at a first speed. A rotary cutting station receives the cathode web from the first feed station and rotatably cuts the cathode web, moving at the first speed, into a series of cathode sheets. A second feed station feeds an electrolyte web at a second speed greater than or equal to the first speed. A first rotary lamination station receives the electrolyte web and the cathode web. The first rotary lamination station rotatably laminates each of the cathode sheets moving at the first speed with the electrolyte web moving at the second speed to produce a first laminate structure having a space between adjacent cathode sheets. A third feed station feeds a web (third web) of a material. A second rotary lamination station receives the third web and the first laminate structure. The second rotary lamination station rotatably laminates the third web with the first laminate structure such that the cathode sheets are disposed between the electrolyte web and the third web.
The cathode web, according to one configuration, includes a number of down-web directed rows of the cathode layered structure. The rotary cutting station in this case cuts the cathode web in a cross-web direction to produce a matrix of the cathode sheets. The material of the third web may comprise an electrical insulator or a solid electrolyte.
In general terms, the space between adjacent cathode sheets is typically a function of the first speed of cathode web movement relative to the second speed of the electrolyte web. More specifically, each of the cathode sheets is defined by a length, and the rotary cutting station comprises a rotary die. The length of each cathode sheet in this case is a function of the first speed of cathode web movement relative to the second speed of the rotary die. The rotary cutting station, for example, includes a rotary die. The rotary die includes at least one rotary die blade separated by a circumferential blade spacing (D). The space (S) between adjacent cathode sheets is a function of the first speed (W1) of cathode web movement relative to the circumferential die blade spacing (D) and the second speed (W2) of the rotary die. The space (S) between adjacent cathode sheets is characterized by an equation S=D((W2/W1)xe2x88x921) in this case.
According to yet another embodiment of the present invention, an apparatus for producing a series of thin-film electrochemical cell structures includes a first feed station that feeds a half-cell web at a first speed. The half-cell web comprises a cathode sheet layer comprising a series of spaced cathode sheets disposed between a solid electrolyte layer and a third layer. The solid electrolyte and third layers respectively extend across gaps defined between the spaced cathode sheets. A second feed station feeds a web (lithium web) of lithium material. A rotary lamination station receives the half-cell web and lithium web. The first rotary lamination station rotatably laminates the half-cell web with the lithium web to produce a unit cell structure. A cutting station receives the unit cell structure. The cutting station cuts through the unit cell structure at respective locations in alignment with the gaps defined between the spaced cathode sheets to produce a cut unit cell structure.
The cutting station typically includes a rotary die that rotatably cuts through the unit cell structure at the respective locations in alignment with the gaps defined between the spaced cathode sheets. The electrolyte web may include a carrier web, in which case the cutting station cuts through the respective lithium, third, and electrolyte webs, but does not cut entirely through the carrier web.
The cathode web, according to one configuration, includes a number of down-web directed rows of the cathode layered structure, in which case the rotary cutting station cuts the cathode web in a cross-web direction to produce a matrix of the cathode sheets.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.